Vention's Blog

How-to-Guide - Troubleshooting Linear Axis Direction

Motor Moves in Only One Direction

This blog discusses a problem with the motor moving in one direction but not the other.

There are 3 possible causes for a motor connected to the MachineMotion controller to move in one direction (clockwise/counterclockwise) but not the other.

A missing or defective end-stop sensor

Inappropriate homing of the axis

Defective hardware

Missing or Defective End-Stop

The objective of the end-stops is to constrain the movement on the axis. For safety reasons, a disconnected or defective end-stop is interpreted by MachineMotion as an indication of the end of the axis. Therefore, the controller will not allow any movement in the direction towards the missing or defective end-stop.

Figure 1. Sensors positions in normal axis mode

Figure 2. Sensors positions in reverse axis mode

Figure 3. MachineMotion end-stop sensor connectors

Homing Not Completed Properly

MachineMotion maintains the position of the linear axis internally. This position is initialized by a proper homing operation. If the homing position is not properly initialized, MachineMotion may not allow movement in the negative direction. If the homing position is wrongly set, movement in the negative direction beyond the homing point is prevented by the system.

Figure 4. Single Axis homing

Inaproppriate homing can be caused by:

a disconnected or defective end-stop sensor;

a system that did not perform homing

Defective Hardware

The motors are controlled with the following 3 signals:

enable => (used to energize the motor)

step => (to ask the motor to move by a single step/micro-step)

direction => (to control the motor direction clockwise or counterclockwise)

enable

step

direction

Motion Controller

Motor Driver

Motor

Figure 5. Step motor internal hardware connections

A defective connection for the direction signal would cause any movement to always be done in the same direction. That is, both positive and negative movement with interpreted as either always positive or always negative.

Note that this type of defect is improbable and is not analyzed in the troubleshooting flowchart.

Troubleshooting Flowchart for Axis Moving in Only One Direction

To troubleshoot, you will need to access the Control Center application included in every MachineMotion controller. Perform the following steps to launch the 1-axis application:

Connect the USB cable of MachineMotion to your PC (or MAC);

Open your browser and type the following in the URL field:

192.168.7.2:8888 for Windows and Linux computers

192.168.6.2:8888 for Mac (OSX) computers

Run the "1-Axis Linear Motion" application

The trouble shooting example discusses a 1-axis system. Multi-axis system can be trouble shoot similarly using the 2 or 3 axes application.